Adobe Digital Editions 4.5.6: Where to find this version for download?

In search of the older version 4.5.6 of Adobe Digital Editions, but it cannot be found.

Is it still somewhere out there?

Why do I want to get it?

The AD 4.5.7 version just causes troubles. It crashes almost every time when I work with it: downloading an e-book, deleting an e-book, copying an e-book to my e-book reader, or just when I stare on the monitor.

Also, it looses the authentication every now and then. I lent an e-book from my library, want to download it. After the usual crash I copy the e-book to the reader. And it cannot be opened, because I've no right to do it. So I delete the e-book, restart the computer after the ADE crash, delete the authentication, restart the computer after the second crash, delete the authentication once again, re-authenticate again, download the e-book once again. Sometimes it works. So I add another e-book. All is well. At last, this is what I hope.

After a few days the authentication is gone, ADE crashes again and I have to delete, restart, and re-authenticate again.

I think the last few weeks I've authenticated about 10 times.